Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties which plugs r u running?

which plugs r u running?

Post Wed Jun 09, 2021 7:08 am

Posts: 176
what r the pros and cons about asbestos gaskets on aluminum heads.
i been using the copper items on my aluminum for decades. always thought the asbestos items were a less desireable choice. never saw mention of them in the Victory Library write ups.

the cppoer slabs on my Chief were claimed to be far superior. what am imissing?

Post Fri Jun 11, 2021 12:47 pm

Posts: 3526
Location: Central Illinois, USA
You really should seriously start thinking for yourself, Servitrike...

Did either HD or Indian ever produce copper gaskets for their aluminum heads?
Copper, even annealed. is still harder than aluminum. and are known to beat their shadows into aluminum heads. The gaskets might be "reuseable", but what happens when the heads have nothing left to mill?

If it takes heat paint to seal them, who needs as gasket? (Said the designers of the K Model...!)

Once again please consider: Do you want to conduct heat from the head to the cylinder, or insulate?


Post Fri Jun 11, 2021 7:25 pm

Posts: 176
that was rude and uncalled for.
i come here because it appears to be a place where enthusiasts help others in the hobby.
i am not a metallurgist.
i do not know if seperating the head from the cylinder is a plus or not.
u are one of the most respected names on this board as i see it.
such a retort from u is beneath the reputation u have.
maybe ur having a bad day?

i would think passing the heat to the head would be a good thing.
i can understand what u describe about wearing the heads off.
my expreience. .
i have had my Servi since 92. i have always used copper gaskets. i have never seen any wear on the heard. they are bolted securely togethjer, rite?
i have only in the past few weeks seen info saying copper is bad for aluminum heads. and while my expreience tells me it is wrong, i wondered if there is something i was ignorant of. i asked here because i doubted myself.
i did not deserve to be insulted by u.

Post Sat Jun 12, 2021 6:35 am

Posts: 3526
Location: Central Illinois, USA
servitrike wrote:
....i would think passing the heat to the head would be a good thing.

The head is hotter than the cylinder, Servitrike.


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Post Sat Jun 12, 2021 8:00 am

Posts: 176
and u have proved that it is better to search for water in the well instead of collecting dew drops from the lawn.

so i had it backwards i thought the heat was in the cylinder and the enlarged fins on the head were to help extract the heat outward. and the copper faciltated that process.
i assume the asbestos gaskets insulate the head from the cylinder. theory being to protect the cylinder and possibly extend its lifespan? would that be correct?

if so?
why would they not be recommended for the stock iron heads?

i used to have problems with asbestos gaskets sealing on my Chief.
i was recommended to get the thick copper slab gaskets and never had that sealing problem again.

Post Sat Jun 12, 2021 9:06 am

Posts: 3526
Location: Central Illinois, USA
Let us remember, Servitrike,...

Flattys run hot on purpose. Their optimum temperature is a hundred degrees higher than an OHV.

The pistons are hammers, and the heads are anvils, upon which hydrocarbons are cracked to release their energy.
Cast iron is extremely durable, maintains heat for efficiency, and actually 'rebounds' more power because its dense. Soft aluminum absorbs some power, but dissipates excess heat to the air better, yet takes longer to warm up.

So you can see why utility machines favored cast iron, and machines with a wider range of duty favored aluminum. Workhorse machines required torque at low RPM (why do you think they had tiny carbs and manifolds?), and really didn't see the spikes of demand that "highway" machines require.

Please ask yourself if you think a thoroughbred would pull your load as well as a plow horse. And for how long?

PS: With heads and cylinders properly dressed 'flat', the only head gaskets I have ever had ANY problem with at all, showing leaks before the motor was even fired... were copper. And that was with cast iron heads!!

Post Sat Jun 12, 2021 12:45 pm

Posts: 176
then the idea of the copper gaskets on the iron heads is to allow the heat all around for a complete"rebound" of power?

thank u for the details.
when i asked the question, i was hoping to understand the WHY of different gaskets. u have graced me with some semblence of what i was searching for.

that leads me to 2 more questions. . .

should the aluminum paint be used on the asbestos gaskets?

how did the copper gaskets get to be the prefered choice?
anybody i talk to use using the copper ones.

Post Sat Jun 12, 2021 1:33 pm

Posts: 3526
Location: Central Illinois, USA
servitrike wrote:
then the idea of the copper gaskets on the iron heads is to allow the heat all around for a complete"rebound" of power?

Not really, Servitrike,

The "rebound" is like if you drop a hammer on a chunk of cast iron and watch the bounce, compared to dropping it on a block of cast aluminum, where the bounce is much less. That's why "billet" heads were so popular in the performance auto industry, because they are denser than cast.
Applies to the pistons too, if you consider cast vs. forged. Its always a give-and-take.

The gasket either seals or it doesn't, and insulates to varying degrees. The question remains: Do we want to encourage head heat to pass to the cylinder? Or dissipate to the air independently?

Heat paint can't hurt much. That's all K Models used!
If it is critical to sealing a copper gasket, then just paint should be enough.

The only reason that I can imagine for the popularity of copper gaskets from vendors is obvious: profit margin.

If anyone has genuine OEM gasket info to share, we all should appreciate it!


Post Sat Jun 12, 2021 3:31 pm

Posts: 1423
Location: Ojo Caliente,NM,USA
I'm gonna have to say that empirically how that the combustion responds to the differences in heat transfer would be the only important measurement. Old photos and conjecture aside they seem slightly more knock resistant with the same fuel with copper. So I feel that the consistent thickness so I can set the squish closer is more important for me. When they designed these engines spongey squishy asbestos was the conventional choice! So unless we can find someone to finance an engineering study of thermal flows and dyno-ed knock resistance with hundreds of variables changed for each gasket maybe even brand of both types. I suppose we will have to agree to disagree.

Post Sat Jun 12, 2021 8:07 pm

Posts: 176
so u have had positive results using the copper pieces with aluminum heads i take it?

and to back up just a bit. . u take a stance of agree to disagree. . .
i did not get a sence that Cotten was making a preference. seemed to me he was presenting a theory and promoting me deciding for myself which way i would care for my own engine.

given that, i appreciate u speaking to this. knocking is not something i would have thought of in gasket application.

Post Sun Jun 13, 2021 3:00 pm

Posts: 3526
Location: Central Illinois, USA
Just how high of compression are you running, Dusty?


Post Sat Jun 19, 2021 11:12 am

Posts: 176
Dusty-Dave wrote:
I have been annealing even unused solid copper. Then painting it with aluminum paint and assembling while still wet for years with no problems. I assume that you lightly sand the tops of the jugs and the heads with the sandpaper stuck to either a surface plate or thick glass that shows no optical distortion.

is this the type of aluminum paint u refer to? ... 27&sr=8-4#

or this? ... 0DER&psc=1


Post Sat Jun 19, 2021 11:18 am

Posts: 176
itz starting to smell like aluminum paint is one of those things that have been made illegal in CA. got any alternate suggestions?

Post Sat Jun 19, 2021 7:26 pm

Posts: 4
Permatex makes a spray for copper gaskets.

Post Sat Jun 19, 2021 8:53 pm

Posts: 176
thank u. .

i saw info on that a few hours ago. it is stated to be rated to 500 Deg.
according to the diagram Cotten posted recently, that is a bit shy.
i also found reference to a copper RTV silicone that is rated to 750 Deg. haven't found that on a shelf yet.


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